- HIGH-1: add `filters` field (mirrors FederationScope PRD §8.1) and `rate_limit` stub (PRD §9.1) to FederationCapabilitiesResponseSchema; M4 populates remaining/reset_at - MED-3: tighten supported_verbs from z.array(z.string()) to z.array(z.enum(FEDERATION_VERBS)) closed enum - Add 10 new test cases covering filters shape, rate_limit full/minimal/absent/invalid, and invalid verb rejection Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>